Multiple stage tractor propulsion vehicle

ABSTRACT

A multiple stage orbital delivery vehicle that uses tractor propulsion to launch the vehicle into space. Only the upper stage of the vehicle includes an engine and avionics allowing the lower stages to be only liquid propellant tanks that may be dumped when empty. The liquid propellant may be either monopropellant or bi-propellant. The upper stage may include multiple nozzles that burn the propellant. Alternatively, the upper stage may include an aerospike engine instead of nozzles. The multiple stage orbital delivery vehicle may be air launched from an airborne aircraft or may be launched from the ground.

RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 13/562,637 filed Jul. 31, 2012, and entitled “MULTIPLE STAGETRACTOR PROPULSION VEHICLE,” the disclosure of which is herebyincorporated by referenced in its entirety.

BACKGROUND

1. Field of the Disclosure

The embodiments described herein relate to a multiple stage orbitaldelivery vehicle that uses tractor propulsion.

2. Description of the Related Art

Multiple stage rockets have been used to launch orbiting devices, suchas satellites, in the past. These have included both ground and airlaunched systems. However, the multiple stage rockets are complex,requiring both engines and control actuation systems to steer eachstage. These control systems typically utilize actuators in both thepitch and yaw control planes to point the engine nozzle in a methodreferred to as thrust vector control, and require either electrical orhydraulic power sources which are added cost and complexity. Each stagehas to be ignited as the lower stage is dropped from the vehicle. If astage fails to ignite, the vehicle may not be successful in deliveringthe satellite into orbit. Further, conventional small multiple stagerockets often use solid propellant stages, which are heavier, lessefficient, and more expensive than liquid propellant. Once solidpropellant has been ignited it is difficult to stop the combustion untilthe entire propellant has been consumed unless higher complexity pintletechniques are used. Varying thrust or throttling the thrust level isalso a challenge for solid propellant rocket motors.

Further, launch vehicle overall reliability is a function of part count,and increasing the launch vehicle reliability needs to be addressed byeither increasing the reliability of individual components with anassociated expense, or else reducing the number of components.

SUMMARY

The present disclosure is directed to a multiple stage orbital deliveryvehicle that uses tractor propulsion and overcomes some of the problemsand disadvantages discussed above. The present disclosure is directed tothe simplicity of a multi-stage launch vehicle employing only a singleset of engines resulting in a lower overall part count, higherreliability, and lower cost compared to multiple stages each havingseparate engines and steering actuation systems. These advantages aremagnified for smaller payload and air launched systems since the cost ofengines, steering actuation, and support subsystems for each stage candominate the total costs for smaller launch systems. The reliability ofa simpler, lower part count implementation, particularly one employingmonopropellant, is lower cost than multiple stages each with their ownpropulsion designed for the same level of reliability.

One embodiment of a multiple stage orbital delivery vehicle comprises afirst stage releasably connected to the orbital delivery vehicle. Thefirst stage includes a first fuel tank and first fuel system. The firstfuel system may include a first fuel line. The orbital delivery vehicleincludes a second stage including a second fuel tank and a second fuelsystem. The second fuel system may include second fuel line inreleasable fluid communication with the first fuel line of the firstfuel system. The second stage comprises one or more engines in fluidcommunication with the first and second fuel systems. The one or moreengines use fuel from the first fuel tank or the second fuel tank. In anembodiment, only a single stage of the orbital delivery vehicle includesan engine.

The multiple stage orbital delivery vehicle may further comprise apayload bay that may be selectively opened. The multiple stage orbitaldelivery vehicle may further comprise a spacecraft positioned in thepayload bay. The first fuel tank and the second fuel tank may be adaptedto contain a liquid propellant, which may be a monopropellant or abi-propellant. The second fuel line may include a valve to preventleakage of fuel from the second fuel tank upon the disconnection of thefirst stage from the orbital delivery vehicle. The orbital deliveryvehicle may include multiple engines each having a nozzle spaced aroundthe exterior of the second stage. The orbital delivery vehicle mayinclude a single engine having multiple nozzles spaced around theexterior of the second stage. The orbital delivery vehicle may include aguidance, navigation, and control system configured to control theoperation of the engine(s).

The engine of the orbital delivery vehicle may be an altitudecompensating nozzle engine, suitable engines may include a linear,curvilinear, annular, or toroidal aerospike engine. The engine of theorbital delivery vehicle may comprise an aerospike engine including anannular combustion chamber, throat, and nozzle. The nozzle of theaerospike engine being located around the exterior of the second stage.The nozzle of the aerospike engine may include multiple septums dividingthe nozzle into multiple sections.

The multiple stage orbital delivery vehicle may further comprise a thirdstage releasably connected to the orbital delivery vehicle below thefirst stage. The third stage may comprise a third fuel tank and a thirdfuel system. The engine(s) of the orbital delivery vehicle may use fuelfrom the third fuel tank when the third stage is connected to theorbital delivery vehicle, may use fuel from the first fuel tank when thethird stage has been disconnected from the orbital delivery vehiclewhile the first stage is connected to the orbital delivery vehicle, andmay use fuel from the second fuel tank when the first stage has beendisconnected from the orbital delivery vehicle. The engine(s) of theorbital delivery vehicle may be adapted to use fuel from any fuel tankthat is connected to the orbital delivery vehicle. The engine may beadapted to use fuel from fuel tanks in a specific order or may beadapted to use fuel simultaneously from any fuel tank connected to theorbital delivery vehicle. The guidance, navigation, and control systemmay control the use of fuel by the engine(s) from the fuel tanksconnected to the multiple stage orbital delivery vehicle.

The multiple stage orbital delivery vehicle may further comprise a firstoxidizer tank and first oxidizer system in the first stage and a secondoxidizer tank and a second oxidizer system in the second stage. Thefirst oxidizer system may comprise a first oxidizer line and the secondoxidizer system may comprise a second oxidizer line. The second oxidizerline may be in releasable fluid communication with the first oxidizerline. The engine(s) of the multiple stage orbital delivery vehicle mayuse a combination of fuel and oxidizer from the first fuel tank and thefirst oxidizer tank or from the second fuel tank and the second oxidizertank. In an embodiment, the engine(s) of the multiple stage orbitaldelivery vehicle may use a combination of fuel and oxidizer from thefirst fuel tank and the first oxidizer tank when the first stage isconnected to the orbital delivery vehicle and use a combination of fueland oxidizer from the second fuel tank and the second oxidizer tank whenthe first stage has been disconnected from the orbital delivery vehicle.

One embodiment is a method of launching a multiple stage orbitaldelivery vehicle. The method comprises using fuel from a first fuel tankof a lower stage of the orbital delivery vehicle in an engine connectedto an upper stage of the orbital delivery vehicle. The lower stage isreleasably connected to the orbital delivery vehicle. The methodcomprises disconnecting the lower stage from the orbital deliveryvehicle and using fuel in the engine from a second fuel tank located inthe upper stage of the orbital delivery vehicle. The lower stage may bedisconnected from the multiple stage orbital delivery vehicle when thefirst fuel tank becomes empty of fuel. The lower stage may bedisconnected from the multiple stage orbital delivery vehicle before itbecomes empty of fuel. For example, the lower stage may be disconnectedupon the vehicle reaching a predetermined altitude or after apredetermined amount of time has elapsed.

The method may further comprise dropping the orbital delivery vehiclefrom an airborne aircraft. The method may further comprise using fuelfrom a third fuel tank in the engine after disconnecting the lower stagewith the third fuel tank being located in a middle stage between thelower stage and the upper stage of the orbital delivery vehicle. Theengine may be adapted to use fuel from the third fuel tank prior todisconnecting the lower stage from the orbital delivery vehicle. Theengine may be adapted to use fuel from any fuel tank that is connectedto the orbital delivery vehicle. The method may include disconnectingthe middle stage from the orbital delivery vehicle prior to using fuelfrom the second fuel tank in the upper stage of the orbital deliveryvehicle. The middle stage may be disconnected from the multiple stageorbital delivery vehicle when the third fuel tank becomes empty of fuel.The middle stage may be disconnected from the multiple stage orbitaldelivery vehicle before it becomes empty of fuel. For example, themiddle stage may be disconnected upon the vehicle reaching apredetermined altitude or after a predetermined amount of time haselapsed.

The method may include opening a payload bay of the upper stage andlaunching a spacecraft from the payload bay. The method may includeflowing fuel through a first fuel line in the lower stage and through asecond fuel line in the upper stage to the engine(s). The method mayinclude flowing fuel through a first fuel line in the lower stage andthrough a second fuel line in the upper stage to the engine(s) andflowing an oxidizer through a first oxidizer line in the lower stage anda second oxidizer line in the upper stage to the engine(s).

One embodiment of a multiple stage orbital delivery vehicle comprises afirst stage comprising a first fuel tank and a first fuel system and asecond stage comprising a second fuel tank and a second fuel system. Themultiple stage orbital delivery vehicle comprises one or more engines influid communication with the first fuel tank and the second fuel tank.The one or more engines are adapted to be shared by the first stage andthe second stage. The multiple stage orbital delivery vehicle mayfurther comprise a third stage comprising a third fuel tank and a thirdfuel system. The third stage may be adapted to share one or more engineswith the first stage or the second stage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an embodiment of a launch system for a two-stage orbitaldelivery vehicle.

FIG. 2 shows an embodiment of a two stage orbital delivery vehicle withthe lower stage connected to the upper stage.

FIG. 3 shows an embodiment of a two stage orbital delivery vehicle withthe lower stage disconnected from the upper stage.

FIG. 4 shows an embodiment of an upper stage of a two stage orbitaldelivery vehicle with the fairings being jettisons away to reveal thepayload.

FIG. 5 shows an embodiment of an upper stage of a two stage orbitaldelivery vehicle with the payload being launched from the upper stage.

FIG. 6 shows a partial cross-section view of an embodiment of a twostage orbital delivery vehicle.

FIG. 7 shows a partial cross-section view of an embodiment of amulti-stage orbital delivery vehicle.

FIG. 8 shows a partial cross-section view of an embodiment of amulti-stage orbital delivery vehicle that includes an aerospike engine.

FIG. 9 shows a partial cross-section view of an embodiment of a twostage orbital delivery vehicle adapted to use a bi-propellant.

While the disclosure is susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and will be described in detail herein. However,it should be understood that the disclosure is not intended to belimited to the particular forms disclosed. Rather, the intention is tocover all modifications, equivalents and alternatives falling within thescope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

FIG. 1 shows one embodiment of a launch system 500 comprising anoptional launch assist aircraft 510 carrying a multiple stage orbitaldelivery vehicle 100. In the illustrated embodiment, the optional launchassist aircraft 510 comprises a Boeing F-15 Eagle fighter aircraft,although those of ordinary skill in the art will appreciate that theoptional launch assist aircraft 510 may comprise a wide variety of othersuitable aerial vehicles. In some embodiments, the multiple stageorbital delivery vehicle 100 is launched from the optional launch assistaircraft 510 after obtaining a predetermined altitude to assist in thelaunch of the multiple stage orbital delivery 100 into orbit. In otherembodiments, the multiple stage orbital delivery vehicle 100 is adaptedto launch off the ground and obtain orbit without the assistance of theoptional launch assist aircraft 510.

FIG. 2 shows an embodiment of a multiple stage orbital delivery vehicle100 that includes a first or lower stage 10 connected to a second orupper stage 20. The depiction of two stages is for illustrative purposesonly, as the multiple stage orbital delivery vehicle 100 may includevarious number of stages necessary for the vehicle 100 to obtain orbit.The upper stage 20 includes one or more engines 25 that burn fuel toprovide thrust in launching the multiple stage orbital delivery vehicle100 into orbit. The multiple stage orbital delivery vehicle 100 mayinclude a single engine having multiple nozzles around the perimeter ofthe vehicle. The engine(s) 25 may be located around the perimeter of thevehicle 100. The number of engines 25 and the spacing around theperimeter of the vehicle 100 may be varied as would be appreciated byone or ordinary skill in the art having the benefit of this disclosure.

In one embodiment only a single stage of the multiple stage orbitalvehicle 100 includes an engine 25 (or a plurality of engines 25). Thesingle stage that includes an engine 25 is the upper stage 20. In someembodiments (not shown), the upper stage 20 includes a single engine 25with a plurality of nozzles connected to the single engine 25. In someembodiments, two stages may share an engine or engines located on theupper stage. With only the upper stage 20 including an engine 25, thedesign of the multiple stage orbital delivery vehicle 100 canadvantageously be simplified. One or more lower stages 10 can simplycomprise fuel tanks that are selectively connected to the upper stage 20to provide fuel to the engine(s) 25 in the upper stage 20. Once a lowerstage 10 is empty of fuel, the lower stage 10 may be dropped from themultiple stage orbital delivery vehicle 100. This configuration alsopermits the vehicle 100 to include only one vehicle attitude controlsystem that is located in the upper stage 10 to control the operation ofthe engine(s) 25. The vehicle axial and attitude control system controlsa valve(s) in the engine(s) 25 to control the thrust from eachindividual engine. In operation, the guidance, navigation, and controlsystem 130 (shown in FIG. 6) controls the combustion of fuel in eachengine 25 to adjust the thrust provided by each individual engine 25,thereby controlling the flight of the multiple stage orbital deliveryvehicle 100.

FIGS. 3-5 show the multiple stage orbital delivery vehicle 100 droppingthe lower stage 10 and launching a payload 40. The lower stage 10 istypically dropped after the tank in the lower stage 10 has become empty,as shown in FIG. 3. Although only one lower stage 10 is shown in theillustrated embodiment, the multiple stage orbital delivery vehicle 100could include multiple lower stages 10 that could also be dropped duringthe flight of the vehicle 100. To launch the payload 40, which may be anorbiting device such as a satellite, from the upper stage 20, the upperstage 20 may include fairings 30 that are jettisoned away from the upperstage 20 to reveal the payload, as shown in FIG. 4. The payload 40 maythen be deployed from the upper stage 20, as shown in FIG. 5.

FIG. 6 shows a cross-section of an embodiment of a multiple stageorbital delivery vehicle 100 that uses a liquid monopropellant fuel. Thelower stage 10 comprises a fuel tank 11 and a fuel line 15 that connectsto a fuel line 21 in the upper stage 20 to provide fuel to the engine(s)25 via lines 22. Once the fuel tank 11 in the lower stage 10 is droppedfrom the multiple stage orbital delivery vehicle 100, the engine(s) 25will begin to burn fuel from the fuel tank 24 in the upper stage 20delivered via fuel lines 21 and 22. The lower stage 10 may be droppedwhen the fuel tank 11 has become substantially empty. However, the lowerstage 10 may be selectively dropped from the multiple stage orbitaldelivery vehicle 100 prior to the fuel tank 11 becoming substantiallyempty. The lower end of the fuel line 21 of the upper stage 20 mayinclude a valve 23, such as a check valve, that prevents downward flowof fuel out of line 21 after the lower stage 10 has been dropped fromthe multiple stage orbital delivery vehicle 100.

The upper stage 20 includes one or more engines 25 that burn fuel fromthe fuel tanks 11, 24 in each stage to produce the thrust to launch themultiple stage orbital delivery vehicle 100 into orbit. As discussedabove, a guidance, navigation, and control system 130 may be used tocontrol the thrust provided by each individual engine 25 to control thevehicle 100 during flight. The engine(s) 25 may be moved to change thethrust vector. The movement of the each individual engine 25 may also becontrolled by the guidance, navigation, and control system 130.

The upper stage 20 includes a payload 40, which may comprise an orbitaldevice such as a satellite, located in a cavity in the upper stage 20.The upper stage 20 could include a nose cap that is jettisoned away withthe fairings 30 to expose the payload 40. In one embodiment, theguidance, navigation, and control system 130 may be integral with thepayload 40 and used to control both the payload 40 after deployment fromthe upper stage 20, as well as the operation of the engine(s) 25 duringthe launch of the vehicle 100.

FIG. 7 shows an embodiment of a multiple stage orbital delivery vehicle200 that includes a first or lower stage 210, a second or middle stage270, and a third or upper stage 220. The multiple stage orbital deliveryvehicle 200 comprises one or more engines 225 located in the upper stage220 only. The lower stage 210 and middle stage 270 do not include anyengines. In the embodiment illustrated in FIG. 7, the lower stage 210includes a fuel tank 211 and a fuel line 215 that is connected to a fuelline 275 in the middle stage 270, which is in turn connected to a fuelline 221 in the upper stage 220. Fuel lines 222 connect fuel line 221with the engines 225 of the upper stage 220.

In operation, fuel can be delivered from the fuel tank 211 in the lowerstage 210 to the engine(s) 225 located on the upper stage 220 via fuellines 211, 275, 221, and 222. Once the fuel tank 211 of the lower stage210 is empty, the lower stage 210 will be dropped from the multiplestage orbital delivery vehicle 200. The engine(s) 225 of the vehicle 200will then begin to burn fuel from the fuel tank 271 of the middle stage270. Fuel from the fuel tank 271 in the middle stage 270 will bedelivered to the engine(s) 225 via fuel lines 275, 221, and 222. Fuelline 275 may include a valve 276, such as a check valve, at the lowerend that prevents the downward flow of fuel out of the end of fuel line275 after the lower stage 210 has been disconnected from the multiplestage orbital delivery vehicle 200. Once the fuel tank 271 of the middlestage 270 is empty, the middle stage 270 may be dropped from the vehicle200. The engine(s) 225 will then burn fuel from the fuel tank 224 in theupper stage 220, with the fuel being delivered to the engine(s) 225 viafuel lines 222 and 223. Fuel line 222 may include a valve 226 thatprevents the downward flow of fuel out of the end of fuel line 222. Theupper stage 220 may then launch a payload device in the same manner asdiscussed above. The multiple stage orbital delivery vehicle 200 mayinclude more stages than three stages as depicted, as would berecognized by one of ordinary skill in the art having the benefit ofthis disclosure.

FIG. 8 shows an embodiment of a multiple stage orbital delivery vehicle300 that includes a lower stage 310 having a fuel tank 311 and fuel line315 that is connected to a fuel line 321 of the upper stage 320. In theembodiment shown in FIG. 8, the upper stage 320 includes an aerospikeengine 325 comprising a combustion chamber 323, throat 324, and nozzle326. Fuel line 321 may be connected directly to the combustion chamber323. Alternatively, an additional fuel line may connect fuel line 321 tothe combustion chamber 323. The throat 324 connects the nozzle 326 tothe combustion chamber 323. The nozzle 326 encircles the entireperimeter of the upper stage 320. The aerospike engine 325 may include aplurality of septums 327 that divide the nozzle 326 into a plurality ofsections. The plurality of sections can be controlled by a navigationand guidance system to adjust the thrust of each section controlling theflight of the multiple stage orbital delivery vehicle 300. As describedabove, the lower stage 310 of the multiple stage orbital deliveryvehicle 300 may be dropped after the fuel tank 311 becomes empty. Thefuel line 321 may include a valve 328 to prevent leakage of fuel afterthe lower stage 310 has been disconnected.

FIG. 9 shows an embodiment of a multiple stage orbital delivery vehicle400 that uses a bi-propellant fuel. The multiple stage orbital deliveryvehicle 400 includes a lower stage 410 connected to an upper stage 420.Additional stages could be connected to the multiple stage orbitaldelivery vehicle 400, as would be appreciated by one of ordinary skillin the art. The multiple stage orbital delivery vehicle 400 comprisesone or more engines 425 located in the upper stage 420 only. The lowerstage 410 does not include any engines.

The lower stage 410 includes an oxidizer tank 411 with an oxidizer line413 connected to a manifold 431 in the upper stage 420. The lower stage410 also includes a fuel tank 412 with a fuel line 414 connected to athe manifold 431 in the upper stage 420. A bulkhead or wall 415 dividesthe lower stage into an oxidizer tank 411 and a fuel tank 412. Inoperation, the oxidizer in the oxidizer tank 411 is delivered to theengine(s) 425 on the upper stage 420 via oxidizer line 413, manifold431, and lines 432 and the fuel in the fuel tank 412 is delivered to theengine(s) 425 on the upper stage 420 via fuel line 414, manifold 431,and lines 432.

Thrust is provided by the combination of the oxidizer and the fuel atthe engine(s) 425 of the upper stage 420. The thrust of each engine 425may be controlled by the guidance, navigation, and control system 430,which may comprise a conventional navigation and guidance system thatmay be incorporated into a payload device in the upper stage 420. Oncethe oxidizer tank 411 and fuel tank 412 are empty, the lower stage 410will be dropped from the upper stage 420. Oxidizer line 413 and fuelline 414 are adapted to break apart when the lower stage 410 is droppedfrom the upper stage 410 with a portion of the lines remaining in theupper stage 410. The upper portion of lines 413 and 414 may includevalves 426 and 427 that prevent the downward flow of oxidizer and fuelout of tanks 421 and 422 upon the separation of the lower stage 410 fromthe upper stage 420. After the lower stage 410 is disconnected from theupper stage 420, oxidizer will be delivered to the engine(s) 425 fromoxidizer tank 421 via oxidizer line 423, manifold 433, and lines 434.Likewise, fuel will be delivered to the engine(s) 425 from fuel tank 422via fuel line 424, manifold 433, and lines 434. A bulk head or wall 428divides the upper stage into an oxidizer tank 421 and a fuel tank 422.The configuration of the oxidizer and fuel tanks is for illustrativepurposes and may be varied.

Although this invention has been described in terms of certain preferredembodiments, other embodiments that are apparent to those of ordinaryskill in the art, including embodiments that do not provide all of thefeatures and advantages set forth herein, are also within the scope ofthis invention. Accordingly, the scope of the present invention isdefined only by reference to the appended claims and equivalentsthereof.

1. A method of launching a multiple stage orbital delivery vehicle, themethod comprising: burning fuel from a first fuel tank of a lower stageof the orbital delivery vehicle in an engine connected to an upper stageof the orbital delivery vehicle while the lower stage is connected tothe orbital delivery vehicle, the lower stage being releasably connectedto the orbital delivery vehicle, wherein the lower stage is coaxial withthe upper stage; disconnecting the lower stage from the orbital deliveryvehicle; and burning fuel in the engine from a second fuel tank locatedin the upper stage of the orbital delivery vehicle.
 2. The method ofclaim 1 further comprising dropping the orbital delivery vehicle from anairborne aircraft.
 3. The method of claim 1 further comprising burningfuel from a third fuel tank in the engine, the third fuel tank beinglocated in a middle stage between the lower stage and the upper stage ofthe orbital delivery vehicle.
 4. The method of claim 3 furthercomprising disconnecting the middle stage from the orbital deliveryvehicle prior to burning fuel from the second fuel tank of the upperstage.
 5. The method of claim 1 further comprising: opening a payloadbay of the upper stage; and launching a spacecraft from the payload bayof the upper stage.
 6. The method of claim 1, wherein burning fuel fromthe first fuel tank of the lower stage further comprises flowing fuelthrough a first fuel line in the lower stage and through a second fuelline in the upper stage to the engine.
 7. The method of claim 1, whereinburning fuel from the first fuel tank of the lower stage furthercomprises: flowing fuel through a first fuel line in the lower stage andthrough a second fuel line in the upper stage to the engine; and flowingan oxidizer through a first oxidizer line in the lower stage and asecond oxidizer line in the upper stage to the engine.
 8. A method oflaunching a multiple stage orbital delivery vehicle, the methodcomprising: burning fuel from a first fuel tank of a lower stage of theorbital delivery vehicle in an engine connected to an upper stage of theorbital delivery vehicle while the lower stage is connected to theorbital delivery vehicle, the lower stage being releasably connected tothe orbital delivery vehicle, wherein the lower stage is below the upperstage in reference to the direction of travel of the orbital deliveryvehicle from the engine; disconnecting the lower stage from the orbitaldelivery vehicle; and burning fuel in the engine from a second fuel tanklocated in the upper stage of the orbital delivery vehicle.
 9. Themethod of claim 8 further comprising dropping the orbital deliveryvehicle from an airborne aircraft.
 10. The method of claim 8 furthercomprising burning fuel from a third fuel tank in the engine, the thirdfuel tank being located in a middle stage between the lower stage andthe upper stage of the orbital delivery vehicle.
 11. The method of claim10 further comprising disconnecting the middle stage from the orbitaldelivery vehicle prior to burning fuel from the second fuel tank of theupper stage.
 12. The method of claim 8 further comprising: opening apayload bay of the upper stage; and launching a spacecraft from thepayload bay of the upper stage.
 13. The method of claim 8, whereinburning fuel from the first fuel tank of the lower stage furthercomprises flowing fuel through a first fuel line in the lower stage andthrough a second fuel line in the upper stage to the engine.
 14. Themethod of claim 8, wherein burning fuel from the first fuel tank of thelower stage further comprises: flowing fuel through a first fuel line inthe lower stage and through a second fuel line in the upper stage to theengine; and flowing an oxidizer through a first oxidizer line in thelower stage and a second oxidizer line in the upper stage to the engine.15. A method of launching a multiple stage orbital delivery vehicle, themethod comprising: burning fuel from a first fuel tank of a lower stageof the orbital delivery vehicle in an engine connected to an upper stageof the orbital delivery vehicle while the lower stage is connected tothe orbital delivery vehicle to provide thrust to move the orbitaldelivery vehicle in a first direction, the lower stage being releasablyconnected to the orbital delivery vehicle, wherein the lower stage isbelow the upper stage in reference to the first direction; disconnectingthe lower stage from the orbital delivery vehicle; and burning fuel inthe engine from a second fuel tank located in the upper stage of theorbital delivery vehicle.
 16. The method of claim 15 further comprisingburning fuel from a third fuel tank in the engine, the third fuel tankbeing located in a middle stage between the lower stage and the upperstage of the orbital delivery vehicle.
 17. The method of claim 16further comprising disconnecting the middle stage from the orbitaldelivery vehicle prior to burning fuel from the second fuel tank of theupper stage.
 18. The method of claim 15 further comprising: opening apayload bay of the upper stage; and launching a spacecraft from thepayload bay of the upper stage.
 19. The method of claim 15, whereinburning fuel from the first fuel tank of the lower stage furthercomprises flowing fuel through a first fuel line in the lower stage andthrough a second fuel line in the upper stage to the engine.
 20. Themethod of claim 15, wherein burning fuel from the first fuel tank of thelower stage further comprises: flowing fuel through a first fuel line inthe lower stage and through a second fuel line in the upper stage to theengine; and flowing an oxidizer through a first oxidizer line in thelower stage and a second oxidizer line in the upper stage to the engine.